Now, we turn to hillary clinton's health scare. The secretary of state has been in a hospital here in new york since sunday, when doctors discovered a blood clot near her brain. We're going to talk to dr. Richard besser in a moment. But sharyn alfonsi is here with the latest on secretary clinton's condition. Good morning. Reporter: Good morning. This morning, clinton is being monitored closely and being given blood thinners to break up that clot. Her family rallying at her bedside, as the normally globetrotting secretary is grounded, forced to spend a fourth day in the hospital. The former president and chelsea clinton leaving the hospital where the secretary is being treated this morning. The secret service stationed outside. Chelsea tweeting, thank you all for sending good thoughts to my mom's way. Grateful to all her doctors. And that she'll make a full recovery. Reporter: It's been three weeks since the secretary of state was last seen in public. During an overseas tour where she picked up a bad stomach virus. Days later, she fainted and got a nasty concussion. An mri refeeling she had a blood clot. Her doctors saying a scan revealed a clot in the vein that's situationed in the space between the brain and the skull right behind the ear. The secretary did not suffer neurologic damage. But it's a setback. She's the most-traveled secretary of state ever. Logging nearly 1 million miles and spending the equivalent of an entire year of her life on a plane. Clinton telling barbara walters, the schedule has taken its toll. You're leaving at the height of your career. Why are you leaving? I've been, as you know, at the highest levels of american and now international activities for 20 years. And I just thought it was time to take a step off. I wanted to take some time. And just really collect myself. Are you exhausted? I am. To be honest, I am. When I do something, I really want to do it. I want to do it to the best of my abilities. Reporter: And the secretary is reportedly in good spirits. Engaging with her doctors and her family, and bill clinton, who is at her side. It is unclear when she will be able to return at the state department before the new secretary of state is sworn in. Elizabeth? Sharyn, thanks so much. Let's turn to dr. Richard besser. Rich, we talked about this on monday morning, about this blood clot. We weren't clear what this was. The news has not been good. It's much more serious than what we thought. This can be dangerous. It's called a transverse sinus th thrombosis. If it breaks off, it can go to her heart and her lungs and be fatal. If it gets bigger, it can go to the top of the head, increasing the pressure on the skull. That can cause stroke and be deadly. Very clear to point out she did not suffer any kind of a stroke. When is she out of the woods for this? She's been in the hospital for several days. At what point is the all-clear given? It wasn't picked up due to neurologic findings. It was a follow-up mri. When she's out of the woods is when her blood is thin. It'santi-coagulated. Those are the things they're watching for. Two things you have to be careful about with blood thinners. If they don't make her blood thin enough, the clot can break off. If they make it too thin, she can bleed into her head or elsewhere in the body. That can be severe. Because she is a front-runner, potentially for the democratic presidential nomination in 2016, a lot of people are watching this closely. What kind of long-term ramifications are there for her health and general well-being? The long-term consequences could be nothing. If they can control this, the clot would go away. She'll be on blood thinners for a period of time. But she'll be able to go back to regular activities. Did this come because of the concussion? The fall? That's not the conclusion. We're going to hear more about that. Let's check back in with josh for a look at the morning

This transcript has been automatically generated and may not be 100% accurate.

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